Stabilized mineral oil composition



rarenrea pepr. 1i. IUI'Z 2,29%,526 STABILIZED ERAL 01L COMPOSITION" Stanley P. Waugh, Westfleld, N. 5., assignor to Tide Water Associated Oil Company, Bayonne, N. J., a corporation of Delaware No Drawing. Application May 22, 1941, Serial No. 394,621

10 Claims.

This invention relates to lubricants and inore particularly to mineral oil compositions containing additive substances imparting special properties thereto.

It is known that certain mineral oils of the motor oil type are unstable when employed in motors operating under heavy duty conditions of service. Such oils when employed as lubricants in internal combustion engines operating at sustained high speeds and hightemperatures deteriorate, probably as a result of oxidation reactions, to produce undesirable reaction products with corresponding reduction in useful service life of the oil. Solid reaction products are deposited upon pistons, ring-grooves and other parts of. the motor in forms known as varnish or sludge, causing impairment of performance and sometimes resulting in breakdown of the motor. Likewise, use of such oils in motors equipped with alloy type bearings results in corrosion of said bearings by action of acidic materials or other substances resulting from oil deterioration.

For the purpose of preventing or lessening the mentioned deleterious effects and to provide satisfactory mineral oil lubricants for the stated purposes it has been the practice to incorporate into the oil various substances to inhibit oil deterioration. It has been found that addition to mineral lubricating oils of certain soaps is beneficial in inhibiting the deposition of varnish or sludge in the motors in which said oils are employed, and various soap compositions have been proposedand used in this connection. It is with such general types of compositions that the present invention is concerned, one important feature or embodiment being mineral oil compositions having incorporated therein certain soaps having inhibitor eifectiveness and certain other agents coacting or reacting with the soap and which may also exert inhibitor action to produce an improved lubricant.

The latter-mentioned agents which are added to mineral oils inconjunction with soaps to probe given ,as examples of suitable compounds of this type. Likewise, other metal salts such as aluminum dioctyl sulfosuccinate are suitable.

In my copending application, Serial No. 389,169,

filed April 18, 1941, I have disclosed the use in mineral oils of compounds of this type and have 1 shown their effectiveness as inhibitorsin lubricants. In general, the classes of salts of esters of sulfodicarboxylic acids and specific members of said classes there disclosed are suitable for use in the present invention.

One important feature of this invention arises from my discovery that these salts of esters of sulfocarboxylic acid exert a solubilizing or stabilizing efiect upon the soap-oil composition. 1- have found that soaps having little or no oil solubility in mineral oil can be brought into solution therein in satisfactory amounts by incorporation of these salts. The resulting compositions are stable as respects any tendency of soap to precipitate out.

This solubilizing or stabilizing property is particularly important in the case of certain soaps of naphthenic acids, for example calcium naphthenates. It has been the practice heretofore in producing mineral oil lubricants, especially paramn base oils containing calcium naphthenate or certain other soaps, to have present acidic substances'since substantially neutral or basic calcium naphthenate as well as certain other soaps are not soluble to any appreciable extent in such mineral oils. Calcium naphthenate is usually dissolved in mineral oils predominantly paraflinic in nature by having present naphthenic acid.

However, the presence of such acids in mineral oils, especially those employed for lubricating engines is undesirable because of the corrosive effect of acids upon metal parts.

By the present invention these soaps can be readily dissolved in mineral oils in eflfective amounts without having present deleterious amounts of acids or the like, and there is pro-. duced improved and stable lubricant compositions having less tendency to cause metal corrosion and characterized by other advantageous properties and characteristics.

Illustrative of what has been stated hereinabove, there may be cited experiments in which calcium naphthenate prepared by treating naphthenic acid derived from petroleum refining operations with more than the theoretical amount of slaked lime was used. Portions of the reaction product consisting of neutral or only slightly acidic calcium naphthenate were heated with mineral oils of various kinds, including viscous lubricating oils of motor grade from crudes of predominately parafiinic nature, to 270 to 300 F. and allowed to cool. No appreciable amount of the prepared calcium naphthenate could be dissolved. In other experiments fresh samples of the same oils were used into which had been dissolved 5 to 10% by weight of sodium dioctyl sulfosuccinate. Upon heating the latter compositions with the prepared calcium naphthenate to the stated temperature and cooling it was found that several per cent by weight'of the calcium naphthenate, based on the weight of the oil, had dissolved. The resulting oil compositions upon cooling were stable solutions.

The exact chemical nature of the oil compositions of this invention is not known. It is quite possible that chemical reaction occurs between the soaps and salts of esters of sulfodicarboxylic acids which are added to the oils, to form a compound or compounds more soluble than the soap, but which performs in the compositions the respective inhibiting functions of both of the added agents. Therefore, although the compositions of the invention are described and claimed herein as containing soaps and the stated salts, such language is also intended to embrace and include compositions containing these substances as reaction products.

The following examples setting forth in detail several mineral oil compositions are illustrative of the invention. These examples set forth compositions prepared from several different mineral oils and indicate the relatively large proportions of soaps that can be incorporated in these various oils by means of this invention.

Example I A dewaxed and decolorized distillate oil having a viscosity of 200 at 100 F., from Pennsylvania crude, was used. 80 parts by' weight of this oil were heated to about 270-300 F. with 10 parts by weight of the calcium naphthenate prepared as stated hereinabove, and the mass was allowed to cool. No appreciable amount of the calcium naphthenate was dissolved. To this mixture there was then added 10 parts by weight of the sodium salt of the dioctyl ester of sulfosucoinic acid and the resulting mixture was heated to the stated temperature and allowed to cool. Upon filtering the resulting composition it was found that about 7 parts of the original l parts of calcium naphthenate had dissolved in the oil.

Example II Another composition was prepared by heating together 85 parts of a Coastal pale oil of 200 viscosity at 100 F., 10 parts of the above described calcium naphthenate and parts of the sodium salt of dioctyl sulfosuccinic acid, all parts being by weight. Upon cooling and filtering it was found that about 6 or 7 parts of the original 10 parts of calcium naphthenate had dissolved. In a similar test, in which 85 parts of the described Coastal pale oil and 10 parts of the described calcium naphthenate were heated together to the stated temperature and cooled, it was found that substantially none of the calcium naphthenate dissolved.

Example III In 90 parts by weight of a decolorized and dewaxed bright stock having a Saybolt viscosity of 154 at 210 F. derived from Pennsylvania crude there were dissolved 10 parts by weight of the sodium salt of dioctyl sulfosuccinic acid and to 95 parts by weight of this solution were added 5 parts by weight of the described calcium naphthenate. The mixture was thenheated to 270-300 F., and allowed to cool. In this case about 2% parts of the original 5 parts of the calcium naphthenate dissolved. Attempts to dissolve this calcium naphthenate in the bright stock without addition of the salt resulted in solution of much less of the calcium naphthenate than in the stated experiment using the described salt.

Example IV calcium oleate and 50% calcium stearate was heated to 280 F. with stirring and allowed to cool. After cooling to room temperature it was observed that the soap still remained in solid undissolved condition in the bottom of the vessel.

A second mixture consisting of 93 parts by weight of the coastal pale oil just described, 2 parts by weight of the neutral soap mixture just described and 5 parts by weight of the sodium saltof dioctyl sulfosuccinic acid, was heatedto 280 F. and then allowed to cool to room temperature. Observation of the cooled product showed it to be a thickened semi-fluid composition containing no solid material. All of the soaps added had dissolved. This composition is useful in grease making and for other purposes requiring a semi-fluid lubricant product.

It will of course be understood that the above examples are given merely for illustrative purposes to indicate the relatively large amounts of soaps whichcan be dissolved in various oils by use of the salts of esters of sulfocarboxylic acids, In the case of lubricating oils for use in lubrication of internal combustion engines the calcium naphthenate or other soap inhibitor is generally effective when incorporated in amounts on the order of about 1% or less. It is clear from the above examples that such eifective amounts of neutral or substantially neutral soaps can be readily dissolved to form motor oils accord ing to the teachings of this invention.

Example V To 159 grams of a motor oil of S. A. E. 20 grade there was added 1 gram of the substantially neutral calcium naphthenate prepared as described hereinabove and 0.39 gram of the sodium salt of the dioctyl ester of sulfosuccinic acid, and the mixture was heated to about 250 F. to 300 F. and allowed to cool to room temperature. There resulted a clear solution containing all of the added materials. The oil used was a dewaxed and decolorized blend of about 77% paraflinic base distillate and about 23% parafilnic base bright stock and was characterized by 29 to 31 gravity, 425 F. flash point, 20 F. pour point, 285/315 viscosity at F., 53/55 viscosity at 210 F. and carbon residue of 0.50. Previous tests had shown that the stated prepared calcium naphthenate per se was substantially insoluble in this oil.

This lubricant composition was subjected to a modified Indiana oxidation test. In this test a weighed portion of a cadmium-silver alloy hearing measuring approximately 1 inch by 3% inches is suspended by an iron wire into a glass vessel containing the test oil so that the bearing strip is completely submerged in the oil and the oil is heated at a temperature of 342 F. for 70 hours while bubbling air through the oil at a rate of 10 liters per hours. At the end of this time the bearing strip is removed, cleaned of oil and reweighed. The loss in bearing weight over the original weight is an indication of the corrosiveness of the lubricant tested.

The loss in weight of the bearing strip in the described test, using the S. A. E. 20 oil containing none of the added materials, was approximately 1.2 grams. In contrast thereto, the loss of weight of the bearing strip in the test using the described lubricant composition of this invention was only 0.025 gram.

The results obtained in this accelerated oxidation test clearly indicate the ffectiveness of the composition of this invention in inhibiting corrosion of alloy type bearings.

The method of lubricating internal combustion engines comprising applying to the bearing surfaces thereof the lubricant compositions of the invention is embraced within the scope of the" invention.

I claim:

1. A lubricant composition comprising a hydrocarbon oil having dissolved therein a neutral metal soap of a character not normally soluble in said oil and a sufiicient proportion of a salt of an ester of a sulfocarboxylic acid to solubilize and maintain the soap in complete solution in the oil.

2. A lubricant composition comprising a hydrocarbon oil having dissolved therein a neutral metal soap of a character not normally soluble in said oil and a sufficient proportion of a salt of an ester of a sulfodicarboxylic acid to solubilize and maintain the soap in complete solution in the oil.

3. A lubricant composition comprising a refined petroleum lubricating oil produced from predominantly parafiinic crude having completely dissolved therein a neutral metal soap not normally soluble in said oil and a sufiicient proportion of a salt of an ester of a sulfodicarboxylic acid to solubilize said soap and stabilize the resulting oilsoap solution.

4. A lubricant composition comprising a hydrocarbon oil having completely dissolved therein a neutral alkaline earth metal naphthenate of a character not normally soluble in said oil and a sufficient proportion of a metal salt of the dioctyl ester of sulfosuccinic acid to solubilize and maintain the neutral naphthenate in solution.

5. A lubricant composition comprising a hydrocarbon oil in which there has been completely dissolved calcium naphthenate through the aid of the sodium salt of dioctyl sulfosuccinic acid, said calcium naphthenate being normally insoluble in said oil but being rendered oil-soluble by said sodium salt.

6. Method of completely dissolving normally insoluble neutral soaps in mineral oils which comprises adding to said mineral oils the neutral soap and a salt of an ester of a sulfodicarboxylic acid, said salt acting as a solubilizing agent for said soap.

7. Method of completely dissolving in mineral oils neutral soaps which are normally not appreciably soluble therein which comprises heating a mixture of said mineral oil, said soap and a salt of an ester of a sulfodicarboxylic acid, said salt acting as a solubilizing agent for said soap.

8. Method of producing stable mineral oil-soap solutions which comprises heating together a mineral oil, a neutral soap normally substantially insoluble in said oil and a salt of an ester of a sulfodicarboxylic acid in amount effective to'cause solution of said soap in said oil.

9. A lubricant composition comprising a mineral lubricating oil having completely dissolved therein a neutral alkaline earth metal soap of a fatty acid of a character not normally soluble therein and a proportion of a salt of a dioctyl sulfosuccinic acid sufficient to solubilize and maintain said soap in solution.

10. Method of lubricating an internal combustion engine which comprises applying to the bearing surfaces thereof a lubricant comprising a hydrocarbon oil, a neutral metal soap normally insoluble in said oil and a salt of an ester of a sulfodicarboxylic acid, said salt acting" as a solubilizing agent for said soap.

STANLEY P. WAUGH. 

